1. Field of the Invention
This invention is directed to apertures in semiconductors and more particularly to heterogeneous composite semiconductor structures for enhanced oxide and air aperture formation for semiconductor lasers and detectors and their method of manufacture.
2. General Background and State of the Art
Oxide and air apertures can enhance the performance of semiconductor lasers and detectors. However, such apertures are difficult to implement in material systems that do not accommodate epitaxial incorporation of highly oxidizing materials of sufficient thickness. For example, the oxide aperture technology has found wide use in devices made in the AlGaAs system, but not so for devices made on indium phosphide (InP) because lattice-matched materials on InP do not oxidize fast enough at temperatures not damaging to the material (except for AlAsSb which is unsuitable because it decomposes into metallic Sb as it oxidizes). Fast-oxidizing materials (e.g. AlAs) may be grown on InP in limited thickness, but such thin layers oxidize too slowly and are of a limited use as optical apertures due to the limited thickness.
The prior art shows several attempts at implementing apertures on InP. In one previous implementation (see Zhi-Jie Wang; Soo-Jin Chua; Zi-Ying Zhang; Fan Zhou; Jing-Yuan Zhang; Xiao-Jie Wang; Wei Wang; Hong-Liang Zhu. “Self-aligned current aperture in native oxidized AlInAs buried heterostructure InGaAsP/InP distributed feedback laser,” Applied Physics Letters, vol. 76, (no. 12), AIP, 20 Mar. 2000. p. 1492–4) AlInAs is used as the oxidation layer. AlInAs typically suffers from low oxidation rates, unless cladded by InP as it has been in this implementation. However, such oxidation layers suffer from rough oxide-semiconductor interface, and thus are unsuitable for optoelectronic device applications.
In another implementation (see Yen, J. C.; Blank, H.-R.; Mishra, U.K. “Lateral oxide current aperture for InP-based vertical electron current flow devices: Demonstration using RTD's,” Proceedings IEEE/Cornell Conference on Advanced Concepts in High Speed Semiconductor Devices and Circuits, Ithaca, N.Y., USA, 4–6 Aug. 1997) AlAsSb is used as the oxidation layer. AlAsSb is unsuitable for most optoelectronic and many electronic device applications because it leaves a layer of metallic Sb as it oxidizes.
In an additional implementation of the prior art (see Ohnoki, N.; Koyama, F.; Iga, K. “Superlattice AlAs/AlInAs-oxide current aperture for long wavelength InP-based vertical-cavity surface-emitting laser structure,” Applied Physics Letters, vol. 73, (no. 22), AIP, 30 Nov. 1998. p. 3262–4) thin layers of heavily-strained AlAs on InP are used. However, the layers described in this reference are extremely difficult to epitaxially grow without a significant amount of dislocations and thus, undesirable for most optoelectronic applications.
It is a goal of the present invention to create apertures in material systems, such as InP, that do not usually accommodate epitaxial incorporation of highly oxidizing materials, such as AlAs, of sufficient thickness to adequately provide optical as well as current aperturing. A further goal of this invention includes the creation of various types of apertures, including tapered apertures, of nearly arbitrary thickness and length.